1. Field of the Invention:
The present invention generally relates to a sewing machine for automatically finishing a threefold hem at the bottom of each leg of a pant garment or trousers and, more particularly, to a hemming machine operable, when the trouser leg with its bottom edge having been folded twice inwardly is set on the machine, to automatically fold the double-folded bottom edge of the trouser leg again inwardly to provide a triple-folded bottom edge and then sew it to finish the threefold hem.
2. Description of the Prior Art
In order to avoid the loosening of textile yarns forming a fabric, the bottom edge of each leg of a pant garment or trousers P is, after having been inwardly triple-folded as indicated by M in FIG. 1, sewed to complete the threefold hem. In general, the stitch left marked by sewing threads used to complete the threefold hem extends circumferentially of the trouser leg with the starting and terminating ends of the stitch overlapped a distance of about 30 to 40 mm with each other, as indicated by W in FIG. 1, for the purpose of avoiding any possible slackening of the sewing threads. Moreover, to provide a well-tailored finish, the overlap W of the stitch is generally so designed as to extends an equal distance on respective sides of the inseam K in the trouser leg.
All of these steps of folding the bottom edge of each leg of the trousers P regardless of the number of the folds and sewing the triple-folded bottom edge thereof are carried out manually. More specifically, a needle-worker, before he or she does an actual sewing job to complete the triple-folded hem, has to manually fold the bottom edge of the trouser leg inwardly to form an overlapped bottom edge and, then, to do a job of causing the overlapped bottom edge to engage a guide, positioned forwardly of a presser foot of the sewing machine, for the formation of the triple-fold, followed by a job of actual sewing after the presser foot has been lowered to press the triple-fold between it and a feed dog of the sewing machine. These steps are laborintensive and time-consuming and, therefore, result in the increased cost of trouser making.
In view of the foregoing, a device has been proposed wherein the threefold hem can be automatically formed in each of the trouser legs, such as disclosed in the Japanese Laid-open Pat. Publication No. 58-138480, published in 1983. According to this prior art device, in order for the stitching, formed circumferentially around the trouser leg, to have its starting and terminating ends overlapping an equal distance on respective sides of the inseam in the trouser leg, utmost care is required for the worker to set the seam at a position a few centimeters preceding the position of the sewing needle. Not only does this require a lot of attentive efforts, but also the position at which the stitch is formed tends to deviate from the expected stitching line.
In addition, in order for the stitch, formed circumferentially of the trouser leg, to have the starting and terminating ends overlapped a distance of about 30 to 40 mm with each other, an accurate measurement of the circumference of the tubular bottom edge of the trouser leg is required. In order to accomplish this, a complicated control is required in that a deviation from a retracted position of a tensioning cylinder to a stretching position thereof has to be measured with the use of a sensor such as an encoder, and the measured value has to be subsequentlY multiplied by a predetermined coefficient to provide the circumference of the tubular bottom edge of the trouser leg for use in the determination of the number of stitches.
Moreover, in the prior art device, since a folding guide is provided at a position preceding the needle and a guide cylinder is fixedly supported at a position preceding the folding guide, there may be created a substantial distance to a supply idle roller positioned rearwardly of the needle and, therefore, it is difficult to insert a trouser leg of relatively small circumference exteriorly onto the device.